Plasticizer and method for manufacturing



Patented May 17, 1938 UNITED STATES PATENT OFFICE PLASTICIZER AND METHOD FOR MANU- FACTURING 'Herman Alexander Bruson,-Philadelphia, Pa., assignor to Riihm & Haas Company, Philadelphia, Pa.

No Drawing. Application September 15, 1934, Serial No. 744,169

14 Claims.

1 ester ofcrotonic acid or an air-blown derivative thereof.

It is already known that a great many high boiling esters of organic acids are useful as plasticizers for cellulosic derivatives. In fact prac- 15 tically all known esters of organic acids are compatible with nitrocellulose to a more or less degree and are capable of giving clear films therewith. Relatively few esters, however, are compatible with cellulose acetate, especially if such so esters are high boiling liquids; the majority of fatty acids with polyhydric alcohols such as triacetin and tributyrin (tributyric glyceride) are 30 readily compatible with cellulose acetate whereas tricaproin is not. On the other hand, triacetin is soluble in water and relatively volatile, and is,

therefore, undesirable in cellulose acetate coatings as a plasticizer, while tributyrin, which is 35 insoluble in water, readily hydrolyzes to form butyric acid which on account of its bad odor is likewise objectionable. l i

Certain esters of dibasic acids, notably, diethyl phthalate, dibutyltartrate or the ethylene glycol 49 monoethyl ether diester of phthalic acid, are

known to be compatible with cellulose acetate,

- but also possess .certainidisadvantages "in the film due to evaporation or hydrolysis. The esters of crotonic acid and monohydric aliphaticalcois physical properties. For example, they are unusually stable towards moisture or hydrolysis and possess an agreeable odor. In addition, they can be treated by the action of heat and air, i. e., they can be blown with air or oxygen-containing gas at an elevated temperature (about 140-l80 C.) to convert them into practically non-volatile viscous oils or solid rubber-like masses of pale color, which are likewise compatible with nitrocellulose or acetylcellulose, if the air-blowingis not carried too far, and which have unusually good plasticizing properties. i

For the purpose of this invention, the purified vacuum-distilled polyhydric alcohol esters of crotonic acid are preferred, such as can be prepared, for example, by heating crotonic acid (preferably in excess) with one of the groupconsisting of glycerol, pentaerythrite,triethylene glycol, HOCH2CH2O-CH2CH2-O-CH2CH2OH,' diethylene glycol HOCHzCHz-OCH2CH3OH, trimethylene glycol OH-CH2CH2-CH2OH, go ethylene glycol, and decamethylene lycol-1, 10.- Of these esters, those made from polyhydric aliphatic' alcohols containing less than 7 carbon atoms are compatiblewith either cellulose acetate or nitrocellulose, whereas those made from higher polyhydric alcohols, such as decamethylene glycol are compatible with nitrocellulose but not with cellulose acetate. The heating is carried out at a temperature of about mil-220C. until the theoretical quantity of water has been split out by the esterification. A black more or less resinous mass is obtained which is useless unless suitably purified. The purification is carried out by distilling-directly in high vacuo whereby unchanged crotonic acid andpartially 36 esterified products come over first, followed by the substantially pure ester. Deleterious resinous by-products of dark color remain behind in the still.

The properties of a few typical estersare as follows:

Glycol dicrotonate from ethylene glyco1)--B. P.

.120 C. at 3mm.

-Diethyleneglycol dicrotonate (from;diethylene-. 5

For use as plasticizers the above esters are mixed either with the cellulosic lacquer in solution, or, for molded plastics, are directly incorporated by kneading as is customary in the art; the quantity to be used depending upon the degree of plastification desired.

The air-blown esters are prepared by heating any of the above purified esters,'either alone or in admixture with each other, to a temperature of about 140-180 C. and passing a current of air or oxygen-containing gas through the liquid until the desired degree of bodying or increase in viscosity has occurred. This operation can be carried out in an inert organic solvent and catalysts to promote the oxidation can be added if desired, such as organic peroxides, or oxides and salts of heavy metals, particularly of cobalt, manganese, vanadium, and the like, which are known to have siccative properties in promoting oxida- 30 tion of drying oils.

The purified crotonic esters of the dihydric aliphatic alcohols are thereby converted into extremely viscous pale yellow oilsresembling blown or heat-bodied castor oil. Upon prolonged blowing with air at elevated temperatures, they do not readily tend to become solid. The purified trihydric, tetrahydric or higher polyhydric alcohol esters of crotonic acid, however, readily go over to very tough, solid rubber-like masses under the same conditions of air-blowing. The latter eventually become insoluble in all organic solvents when the air-blowing is prolonged, but the final product is much tougher, softer and more coherent than analogous linoxyn-like products made by air-blowing the natural drying or semidrying oils. The blown polycrotonates are thus film-forming materials in themselves and can find application as resins in coating compositions of the most diverse nature. For special purposes the purified crotonates described herein can be admixed with natural or synthetic drying oils,

semidrying oils, autoxidizable resins and the like, and the mixture then blown with air at an elevated temperature to produce extremely tough condensation products which are useful in coating compositions, adhesives, and plastics.

Lacquers containing cellulosic derivatives, notably nitrocellulose or cellulose acetate, plasticized with the polyhydric alcohol esters of crotonic acid of the type set forth herein, can be used on wood, metal, paper, leather, textile fabrics, artificial leather, or rubber to produce resistant coatings of good flexibility and adhesion. In general the weight ratio of plasticizer to cellulose derivative varies considerably with the surface and type of coating desired, and can best be determined only by experiment. A ratio of about 1 part by weight of plasticizer to 1 part cellulose derivative gives very fiexible films suitable for use on absorbent surfaces such as leather, whereas, for use on metal surfaces, a ratio of about 0.8 part by weight of the plasticizer will be found sufficient.

It is understood that the term polyhydric alcoho as used herein refers to aliphatic polyhydric alcohols which can be distilled in vacuum without decomposition and is meant to specifically exclude sugars or cellulose itself.

Although the vacuum distilled polyhydric alcohol esters of crotonic acid are good plasticizers for cellulosic derivatives, especially cellulose nitrate and acetate, they may also be used with other organic plastic materials such as phenolformaldehyde resins and analogous brittle resins to toughen them.

It is understood that the above description is given by way of illustration only, and not of limitation, and that deviations are possible within the spirit of the invention the scope of which islimited only by the following claims:

I claim:-

1. An air-blown product of the completely esterified crotonic acid ester of a polyhydric aliphatic alcohol which can be distilled in vacuum without decomposition.

2. An air-blown product of the dicrotonate of a dihydric aliphatic alcohol which can be distilled in vacuum without decomposition.

3..An air-blown product of the tricrotonate of a trihydric aliphatic alcohol which can be distilled in vacuum without decomposition.

4. An air-blown product of the tricrotonate o glycerine.

5. An air-blown product diethylene glycol.

6. An air-blown product of the tetracrotonate of pentaerythrite.

7. The process of preparing plastic materials comprising treating the completely esterified crotonic acid ester of a polyhydric alcohol which can be distilled in vacuum without decomposition with gaseous oxygen at an elevated temperature.

8. The process of preparing plastic materials comprising treating the completely esterified crotonic acid ester of a polyhydric alcohol which can be distilled in vacuum without decomposition with air atl40'to 180 C.

9. The process of preparing plastic materials comprising treating the tricrotonate of glycerine with air at elevated temperatures.

10. The process of preparing plastic materials comprising treating the dicrotonate of diethylene glycol with air at elevated temperatures.

11. The process of preparing plastic materials comprising treating the tetracrotonate of pentaerythrite with air at elevated temperatures.

12. The. process of preparing plastic materials comprising treating the completely esterified crotonic acid ester of a polyhydric alcohol which can be distilled in vacuum without decomposition with gaseous oxygen at an elevated temperature in an inert solvent.

13. The process of preparing plastic materials comprising treating the completely esterified crotonic acid ester of a polyhydric alcohol which can be distilled in vacuum without decomposition with gaseous oxygen at an elevated temperature in the presence of a catalyst.

14. The process of preparing plastic materials comprising treating the completely esterified crotonic acid ester of a polyhydric alcohol which can be distilled in vacuum without decomposition with gaseous oxygen at an elevated temperature in the presence of one of the group consisting of drying oils, semi-drying oils and autoxidizable resins.

HERMAN ALEXANDER BRUSON.

of the dicrotonate of 

